Advanced Lung Cancer Inflammation Index as a Prognostic Inflammation–Nutrition Marker in Appendiceal High‐Grade Pseudomyxoma Peritonei: A 10‐Year Single‐Center Study

Background Pseudomyxoma peritonei (PMP) prognosis remains heterogeneous. Systemic inflammation and nutrition are linked to cancer survival, but their role in PMP is unclear. We aimed to evaluate the prognostic impact of inflammation–nutrition status in appendiceal high‐grade PMP and to develop and internally validate a perioperative prognostic model. Methods We retrospectively included patients with pathologically confirmed appendiceal high‐grade PMP who underwent cytoreductive surgery (CRS) with or without hyperthermic intraperitoneal chemotherapy (HIPEC) between January 2015 and December 2024. Baseline variables included demographics, body mass index (BMI), tumor markers (CEA, CA19‐9, CA125), inflammation–nutrition indices (advanced lung cancer inflammation index [ALI], prognostic nutritional index [PNI], neutrophil‐to‐lymphocyte ratio [NLR], platelet‐to‐lymphocyte ratio [PLR], lymphocyte‐to‐monocyte ratio [LMR], systemic inflammation score [SIS], systemic immune–inflammation index [SII]), prior surgical score (PSS), peritoneal cancer index (PCI), completeness of cytoreduction (CC), HIPEC, pathological subtype, and Ki‐67. Overall survival (OS) was the primary endpoint. Prognostic factors were identified by univariable and multivariable Cox models, and a nomogram was developed and internally validated. Results Among 223 patients (146 females, 65.5%), median age was 59 years, and median OS was 21 months. In the multivariable Cox regression model, independent risk factors for worse overall survival (OS) were high‐grade with signet‐ring cells (hazard ratio [HR] = 2.575, 95% CI 1.749–3.790; p < 0.001), elevated CA19‐9 (HR = 2.189, 95% CI 1.501–3.192; p < 0.001), elevated CA125 (HR = 1.495, 95% CI 1.050–2.127; p = 0.026), high Ki‐67 (HR = 1.976, 95% CI 1.238–3.154; p = 0.004), and an unfavorable CC (CC1–3) (HR = 2.705, 95% CI 1.295–5.648; p = 0.008), while receipt of hyperthermic intraperitoneal chemotherapy (HIPEC) (HR = 0.611, 95% CI 0.377–0.991; p = 0.046) and a high ALI (HR = 0.576, 95% CI 0.398–0.834; p = 0.003) were independent protective factors. The model achieved a C‐index of 0.753, with 1‐, 2‐, and 3‐year AUCs of 0.810, 0.839, and 0.775, respectively. Calibration error was low (≈3%–6%) and decision‐curve analysis showed sustained net benefit across broad threshold ranges. Conclusions The ALI is an independent prognostic marker in appendiceal high‐grade PMP. A nomogram incorporating ALI with tumor and pathological variables enabled reliable perioperative survival prediction with strong discrimination, calibration, and clinical utility.